For the past few years, Andy Robertson has been bombing up and down the left flank for Liverpool, with Kostas Tsimikas acting as his deputy, although the latter is enjoying more game time than expected this season.
Tsimikas has started three of Liverpool's four Champions League games this season - including the 4-0 thrashing of Bayer Leverkusen in midweek - and two of the Reds' last four Premier League games heading into Saturday's clash with Aston Villa.
Slot has suggested that Robertson is still his number one pick, but speaking to Sports Mole, Lynch insisted that Tsimikas deserved to be selected on current form and questioned whether the former's 30 years were catching up to him.
"I think it should be on the basis of performances," Lynch said when asked who should be picked. "And I think this manager has shown so far that he will pick on form. He starts the season with [Jarell] Quansah at centre-half, doesn't he? Because what he's seen in pre-season he likes and then gets to half time of that game against Ipswich and changes it. And then [Ibrahima] Konate keeps the shirt.
"And since then, we've seen Joe Gomez maybe jump up the centre-half pecking order. We've seen competition between Curtis Jones and Dominik Szoboszlai, Luis Diaz and Cody Gakpo.
"So he will pick on form. And I just think if you look at it on the basis of form, then Kostas Tsimikas would deserve to be there. It's an interesting one with the way it's played out, that I think we all assumed Tsimikas starts the Brighton game and therefore he's the first choice.
Why should Tsimikas be picked over Robertson for Liverpool?
"But obviously then, hot on the heels of that, you had Leverkusen and Aston Villa coming up. So I'm not sure it's as clear-cut as that. It's kind of interesting to see what he's going to select around those two games in terms of what that tells us around his choice.
"But for me, I would say on form at the moment that Tsimikas should be ahead of Robertson because I think Robertson is just struggling a little bit. And whether that is, as the manager kind of alluded to, that lack of pre-season is really hurting him or whether it's just kind of age catching up with him after eight years of phenomenal performance. It could well be that.
"But I do think Tsimikas is looking more secure and comfortable and offering more threat going forward and also looking more defensively secure. And so really, if the manager does stick to his principles of picking on form, then for me it should be Tsimikas in that slot."
Robertson is now in the final two seasons of his Liverpool contract - which runs out in the summer of 2026 - and the 30-year-old's recent lack of European starts especially has added fuel to the fire surrounding a possible exit from Anfield.
It has been suggested that Bayern Munich are interested in signing the Scotland international as a replacement for Alphonso Davies, who is expected to join Real Madrid on a free transfer, although a report from Football Insider claims that the Liverpool hierarchy plan to discuss a new contract with Robertson next summer.
However, with the former Hull City man turning 31 next year, and doubts surrounding Tsimikas's ability to hit Robertson's peak levels of performance, Lynch has urged the Reds to sign a new left-back either in January or midway through the campaign.
The Liverpool expert believes that Wolverhampton Wanderers' Rayan Ait-Nouri, Bournemouth's Milos Kerkez and Fulham's Antonee Robinson can fill the Robertson void, although he stressed that there "a lot of good options" in the left-back market.
Liverpool told left-back replacements for 'ageing' Robertson
Asked if Liverpool need to make the left-back position a priority, Lynch added: "Absolutely. It has to be a position that Liverpool sign in either in January or in the summer. I mean, I feel the likelihood of them signing someone there in January is quite low just because they've got two on the books and Liverpool don't tend to really stockpile players in that way. They would probably like to get someone out the door before they sign someone else.
"But it has to be addressed for me. There's a lot of good options out there, even just in the Premier League. I'm thinking Kerkez at Bournemouth, Antonee Robertson at Fulham, Ait-Nouri at Wolves.
"There's some really, really good left-backs out there who have good age, good profile, really good attackers and can defend as well. Really good combination. What they are basically is kind of Robertson when he first joined Liverpool.
"And I just think with Robertson, I think we've probably seen the best of him in a Liverpool shirt, which you kind of feel sad to say, but he's been unbelievable, as I say, for eight years, pretty much. And it was an absolutely bargain signing, but age catches up with everyone. And I think he's particularly brutal in the full-back position because you've got to be up and down, up and down.
"And if you lose a yard, it's just so, so easy to see that. And I do feel that we're seeing that with Robertson. I mean, hopefully proves me wrong and kind of rolls back and has a better season from this point onwards.
"And it is just that pre-season element that's costing. But for me, I think regardless, I really think it's an area Liverpool need to address because, you know, you could say that Tsimikas can step up and be that first choice. But for me, he's always been a really solid backup, but I'm not sure he's not going to touch Robertson's level at his peak.
"And so for me, that's what Liverpool should be aiming for is someone who's just about to hit that level. And like I say, there's a lot of good options out there that they could look at. And I think it's something they should look at the next two transfer windows.
Robertson has been tipped to win his place back in the starting lineup for Saturday's Premier League clash with Aston Villa, where the Reds will endeavour to maintain or increase their two-point lead over Manchester City at the top of the table.